1. Field of the Invention
The present invention relates to a moving image recording apparatus with a stream recording function of a moving image, an electronic camera and a moving image recording method.
2. Description of the Prior Art
In recent, moving-image recording apparatuses are available in the market, in which an input moving image is compressed in real time and a stream recording is executed to record image data on a recording medium. For instance, digital cameras having a moving-image recording function are examples of such moving-image recording apparatus. In general, various sorts of detachable memory cards are used as the recording medium in the digital camera. In a moving-image recording operation, image data is compressed every frame and successively recorded on the memory card and the like. Further, it is general that a user of such digital camera is allowed to select a quality (recorded image quality, “fine”, “normal” and “economy”) of the moving image to be recorded. A recording operation of a moving image in a shooting mode is executed in accordance with plural parameters (mainly, a compression system, compression rate, image size, and frame rate), and these parameters are fixed based on the selected recorded-image quality. Further, data volume to be processed within a certain period of time in the recording operation is almost determined based on the recorded-image quality.
Meanwhile, when the stream recording of a moving image is executed in the digital camera, the following method is employed to perform a long time recording, that is, in such method, a buffer area for recording image data for plural frames is secured in a built-in memory, and previously recorded image data is read out and recorded on the memory card and the frame data is removed from the built-in memory while frame data is being recorded on the built-in memory. In other words, the method uses the built-in memory as a ring buffer.
Further, in the image-recording operation, data volume to be processed within a certain fixed period of time increases as the recorded-image quality is set higher. When a data-writing rate per a unit time exceeds the data-writable rate of the memory card, this can be the cause of loss of the moving image data and/or discontinuity of a sound. The data-writing rate at which data is written on the memory card and the like greatly varies depending on the sort of the memory card. Therefore, the image-recording parameters corresponding to the recorded-image quality are fixed based on the sort of the memory card to be used.